Aetius was the most powerful general in West (magister militum) from 433 until his death in 454.
His greatest opponent was Attila and his greatest victory was the defeat of a Hunnic army under Attila in 451 at the battle of the Catalaunian Fields. As a young man he spent years as a hostage to the Huns, forming a friendship with King Rugila, Attila’s uncle and predecessor. His most reliable troops in the defense of Gaul against the Germans were Huns, and, moreover, Aetius himself married a German bride. Valentinian III assassinated him in 454, despite his loyal service. Such were the ironies of Aetius’s career, ironies that reveal the complexity of Germano- Roman relations in the fifth-century West.
(Source: «Historical Dictionary of Byzantium», by John H. Rosser)